The document is an introduction to CMake, a software tool that manages the build process for C/C++ projects, making it simpler and more organized. It discusses the necessity of a build system, the widespread use of CMake among developers, and provides examples of how to create binaries and libraries using CMake commands. The content emphasizes the benefits of CMake, including cross-platform support and ease of integration with existing projects.

1. Introduction to CMake
Dimitris Platis
dimitris@platis.solutions

2. [grcpp]
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3. About me Dimitrios Platis
● Grew up in Rodos, Greece
● Software Engineer @ Zenseact,
Gothenburg
● Course responsible @ DIT112 & DAT265
Gothenburg University / Chalmers
● Interests:
○ Embedded systems
○ Software Architecture
○ API Design
○ Open source software & hardware
○ Robots, Portable gadgets, IoT
○ 3D printing
○ Autonomous Driving
● Website: https://platis.solutions

4. How about you?

5. What is CMake?
CMake is a software that manages the
way C/C++ projects are built. It has the
ability to simplify the build process of
projects with large or complex code
layouts and is compiler-agnostic.
It is considered the de facto standard for
building C/C++ projects.

6. When is a build
system
necessary?
● Avoid hard-coding paths
● Build a package on more than one
computer
● Support multiple operating systems and
compilers
● Describe how your program is
structured logically, not flags and
commands
Source: An Introduction to Modern CMake

7. Why do you
need to learn
CMake?
● 55 to 80% of C++ developers use it
● The vast majority professional C++
projects use it
● Cross-platform
● Well-supported by IDEs
● Relatively easy to get started with
● Makefiles and building with the command
line simply do not scale

8. Create binaries

9. Create binary with command line
// src/main.cpp
#include <iostream>
int main()
{
std::cout << "Hello World" << std::endl;
return 0;
}
$ g++ src/main.cpp
$ ./a.out

10. Create binary with CMake
cmake_minimum_required(VERSION 3.12)
project(IntroToCmake)
add_executable(hello_world src/main.cpp)
$ mkdir build
$ cd build
$ cmake ..
$ make
$ ./hello_world

11. Generated build/Makefile
# Default target executed when no arguments are given to make.
default_target: all
# The main all target
all: cmake_check_build_system
$(CMAKE_COMMAND) -E cmake_progress_start /home/me/projects/intro-to-cmake/build/CMakeFiles
/home/me/projects/intro-to-cmake/build//CMakeFiles/progress.marks
$(MAKE) $(MAKESILENT) -f CMakeFiles/Makefile2 all
$(CMAKE_COMMAND) -E cmake_progress_start /home/me/projects/intro-to-cmake/build/CMakeFiles 0
# Build rule for target.
hello_world: cmake_check_build_system
$(MAKE) $(MAKESILENT) -f CMakeFiles/Makefile2 hello_world

12. Let's spice things up
// src/greeter.h
#ifndef GREETER_H
#define GREETER_H
void greetClass();
#endif
// src/greeter.cpp
#include "greeter.h"
#include <iostream>
void greetClass()
{
std::cout << "Hello GRCPP" << std::endl;
}
$ g++ src/main.cpp src/greeter.cpp
$ ./a.out

13. CMake allows for structured & version controlled scaling
add_executable(hello_world src/main.cpp
src/greeter.cpp)
$ make
$ ./hello_world

14. Set include path
#include <foo/Foo.h>

15. mv src/greeter.h include/greeter/greeter.h
We want to start including "greeter.h" as
"greeter/greeter.h"
#include "greeter.h" ➡ #include "greeter/greeter.h"
$ g++ src/main.cpp src/greeter.cpp -I include/

16. mv src/greeter.h include/greeter/greeter.h
target_include_directories(hello_world PUBLIC include) $ make

17. Create libraries

18. libgreeter.a (static library)
add_library(greeter src/greeter.cpp)
target_include_directories(greeter PUBLIC include)
add_executable(hello_world src/main.cpp)
target_link_libraries(hello_world PUBLIC greeter)
$ make greeter
$ ls -l libgreeter.a
> -rw-r--r-- 1 me me 3088 libgreeter.a
$ make hello_world
$ ldd

19. libgreeter.so (dynamic library)
add_library(greeter SHARED src/greeter.cpp)
target_include_directories(greeter PUBLIC include)
add_executable(hello_world src/main.cpp)
target_link_libraries(hello_world PUBLIC greeter)
$ make greeter
$ ls -l libgreeter.so
-rw-r--r-- 1 me me 16856 libgreeter.so
$ make hello_world
$ ldd hello_world
libgreeter.so =>
/home/me/intro-to-cmake/build/libgreeter.so

20. Building libraries with CLI
Static library
$ g++ -c src/greeter.cpp -I include/
$ ar rvs greeter.a greeter.o
$ g++ src/main.cpp greeter.a -I include/
Dynamic library
$ g++ -c src/greeter.cpp -I include/ -fPIC
$ g++ -L . src/main.cpp -l greeter -I include/

21. Set compilation flags
🚩🚩🚩

22. Add universal VS target-specific flags
add_compile_options(
-Wall
-Wextra
-Wpedantic
-Werror
)
$ g++ src/main.cpp -Wall -Wextra -Wpedantic -Werror

23. Disable flag(s) for a specific target
target_compile_options (greeter PRIVATE -Wno-pedantic)

24. Configure the build with options

25. Conditional builds
option(BUILD_ALTERNATIVE_GREETER
"Build the alternative libgreeter" OFF)
if(BUILD_ALTERNATIVE_GREETER)
add_library(greeter SHARED
src/alternative_greeter.cpp)
else()
add_library(greeter SHARED src/greeter.cpp)
endif(BUILD_ALTERNATIVE_GREETER)
target_include_directories(greeter PUBLIC
include)
add_executable(hello_world src/main.cpp)
target_link_libraries(hello_world PUBLIC
greeter)
$ cmake .. -DBUILD_ALTERNATIVE_GREETER=ON

26. CMake functions
⚙

27. Customize your build steps
function(configure_test testExecutable)
# Link against gtest library
target_link_libraries(${testExecutable}
gtest gtest_main gmock_main)
# Disable variadic macro warnings
target_compile_options(${testExecutable}
PRIVATE -Wno-gnu-zero-variadic-macro-arguments)
# Create test name as the capitalized form
string(TOUPPER ${testExecutable} testName)
# Add executable to test suite
add_test(${testName} ${testExecutable}
${GTEST_RUN_FLAGS})
endfunction(configure_test)
add_executable(dummy_test DummyTest.cpp)
configure_test(dummy_test)

28. Takeaways
● We covered only the surface
● Easy things are simple with CMake
● Integration with custom build systems or other
libraries is where the trickery begins
● Start using CMake (or equivalent, e.g. Bazel)
even for personal projects

30. Let's keep in touch!
https://www.linkedin.com/in/platisd/
dimitris@platis.solutions
@PlatisSolutions

31. JetBrains lottery
1 year license for any Jetbrains IDE!
1. Go to: http://plat.is/jetbrains
2. If you won, please stick around until I
contact you
3. If you did not win, better luck next time!
Did you know that as a university student you
can get a free JetBrains license anyway?